Since long, the process of Fluid Catalytic Cracking is known to convert high-boiling point, high-molecular weight hydrocarbon fractions of petroleum crude oils to more valuable, lighter fractions gasoline, olefin gases and other products. The feedstock subjected for catalytic cracking is usually heavy gas oil or vacuum gas oil (HVGO) whose long chains break during the process in the presence of the catalyst.
US Patent Application No. 2010/0105974 describes the Catalysts comprising first molecular sieve made up from a small pore zeolite having a pore index between 13 and 26, and a second molecular sieve made up from an intermediate pore zeolite having a pore index between 26 and 30, wherein the first molecular sieve comprises between 5 and 95 wt. % of the catalyst, and the second molecular sieve comprises the remainder of the catalyst for cracking of naptha.
U.S. Pat. No. 5,846,402 also discloses a process for selective catalytic cracking of a petroleum-based feedstock to produce a product having a high yield of liquefied petroleum gas (LPG) and light olefins having 3 to 4 carbons includes providing a fluidized bed reactor which is a high velocity riser, continuously circulating fluidized bed reactor; providing a solid acidic catalyst comprised of: from 1 to 6% by wt, of ultra-stable Y-zeolite; from 8-25% by wt, of Pentasil zeolite which is shape selective; from 0-8% by wt. of an active material Which is bottom selective; from 0-1% by wt. of rare earth constituents; and from 91 to 60% by wt. of nonacidic constituents and binder; charging the fluidized bed reactor with the solid acidic catalyst and the petroleum-based feedstock; and cracking the petroleum-based feedstock in the presence of the solid acidic catalyst in the fluidized bed reactor. The process produces a LPG yield ranging up to 40 to 65 wt. % of the fresh petroleum-based feedstock, a selectivity for the light olefins of at least 40 wt. %, and a selectivity for the LPG of at least 45 wt.
Another U.S. Pat. No. 7,462,275 describes the Fluidizable catalyst comprising 5 to 40 wt. % of medium pore crystalline alumino-silicate, 0 to 10 wt. % of Y type zeolite, 0 to 5 wt. % of non-crystalline acidic material and the remaining being acidic components and binder for production of saturated LPG and off gas.
U.S. Pat. No. 6,455,750 describes the catalyst contains 20-60 wt. % of ZSM-5 molecular sieve having an average pore diameter less than 0.7 nanometer. The catalyst's steam activation Index is greater than 0.75 for the production of C3 and C2 fraction with propylene comprising at least about 90 mol % of C3 fraction and ethylene comprising 90 mol % of C2 fraction from cracked naphtha streams (C5-221° C.).
U.S. Pat. No. 6,656,345, dated Feb. 12, 2003 describes the Zeolite based catalyst selected from the group containing of medium pore zeolites having Silica to alumina ratio>200:1 and pore diameter less than 0.7 nm for the production of light olefins mainly propylene from olefinic hydrocarbon feedstock boiling in the naphtha range (18-220° C.).
Maximum ethylene and propylene yields reported in the patents from olefinic naphtha feedstock is 50 wt. %. Maximum ethylene reported from naphtha feed stream is in the range of 6 to 23 wt. % and propylene is in the range of 20-34 wt. %. Very few patents are related to paraffinic feedstocks. Maximum propylene & ethylene reported in the literature from paraffinic naphtha has been 21 wt. % and 13 wt. % respectively. However, in most of the cases, boiling point of the naphtha is in the range of 20 to 220° C. No Patent related to condensate cracking is obtained. None of the patent uses the catalyst composition having high silica/alumina (>40) ratio Y zeolite for production of light olefins.
The catalyst employed in most of the patents has been pentasil zeolite such as ZSM-5/ZSM-11 based catalyst or the zeolite modified with alkali metals etc. Some of the patents have also disclosed phosphorous to be added in ZSM-5 based catalyst. Even some of the patent considered mixture of ZSM-5 zeolite as well as USY zeolite based catalyst. Some of the patent considered dehydrogenating metal such as Ni, Pt, Pd etc. in the ZSM-5 based catalyst.
Despite various attempts Which have been made with variations in fluid catalytic cracking process and in the catalyst composition, still techniques are continually sought for improving the system in terms of the yield and efficiency.